In the related art, Al or an Al alloy is widely used as a wiring film such as a flat panel display such as a liquid crystal or an organic EL panel, or a touch panel. In recent years, it has been required that the wiring film is miniaturized (has a narrow width) and has a small thickness, and a wiring film having a lower specific resistance than the wiring film in the related art is desired.
Therefore, a wiring film using copper or a copper alloy which is a material having a lower specific resistance than Al or an Al alloy is provided in order to meet the demand for miniaturization and a small thickness of the wiring film as described above.
A sputtering method using a sputtering target is generally used when forming such a wiring film (thin film) of copper or a copper alloy on a substrate.
As the sputtering target described above, a flat sputtering target disclosed in PTL 1 or a cylindrical sputtering target disclosed in PTL 2 has been proposed.
Herein, in the cylindrical sputtering target, an outer peripheral surface thereof is a sputtering surface and the sputtering is performed while rotating the target. Accordingly, sputtering using the cylindrical sputtering target is more suitable for continuous film formation as compared to using a flat sputtering target and excellent efficiency in use of the target is obtained.